Process of converting lead sulfate into lead hydroxid.



PATENTED APR. 18, 1905.

A S. RAMAGE. PROCESS OF CONVERTING LEAD SULFATE INTO LEAD HYDROXID.

APPLICATION FILED DEC. 16, 1904.

lzzzjm pba woypzs Mama WM MUZGSSGS UNITED STATES Patented April 18,1905.

PATENT OFFICE.

ALEXANDER S. RAMAGE, OF DETROIT, MICHIGAN.

SPECIFICATION forming part of Letters Patent N 0. 787,541, dated April18, 1905.

Application filed December 16, 1904:. Serial No 237,165.

To all whom it may concern:

Beit known that I, ALEXANDER S. RAMAGE, a citizen of the United States,residing at Detroit, in the county of Wayne and State of Michigan, haveinvented certain new and useful Improvements in Processes of ConvertingLead Sulfate into Lead Hydroxid, of which the following is aspecification.

When lead sulfate is treated with an equimolecular quantity of sodiumhydroxid in aqueous solution, about ninety per cent. of the lead isconverted into hydroXid. A portion of the lead dissolves in thesodium-hydroxid solution with the production of sodium plumbite, andabout ten per cent. ofthe lead sulfate remains unchanged.

According to the present process lead sulfatefor example. the waste fromsulfuricacid chambersis treated with a suflicient excess of sodiumhydroxid to entirely decompose the sulfate, the preferred excess beingfrom ten to fifteen per cent. About ten per cent. of the lead goes intosolution as sodium plumbite. The solution containing sodium plumbite andsodium sulfate is then separated from the lead hydroxid and treated withlead sulfate in amount sufficient to decompose the plumbite and convertall of the sodium therein into sulfate, the reacting proportions beingone molecule of plumbite to three molecules of lead sulfate. One atom oflead appears as lead hydroxid and threeatoms of lead as basic leadsulfate. The sodium sulfate is recovered from the solution as Glauberssalts, and the basic lead sulfate is treated with an excess of sodiumhydroxid, whereby the major portion of the lead is converted intohydroxid. A part of the lead goes into solution as plumbite and isrecovered as before.

Referring to the accompanying drawings, Figure 1 is a side elevation ofapparatus which may be employed to carry out the process, and Fig. 2shows three equations which represent the principal reactions occurringin the process.

The apparatus illustrated in Fig. 1 comprises tanks 1 2, in which thereactions are effected. Each of these tanks contains a rotary agitator 3and a heating-coil 4:. Valved pipes 5 6 are arranged to deliver thesolutions from the tank 1 or 2 into a lower tank 7, from which they areagain lifted through a pipe 8 by means of an ejector 9 and deliveredthrough valved branch pipe 10 or 11 into-the tank 2 or 1. Dischargepipes 12 13 lead from the bottom of the tanks 1 2. In employing thisapparatus to carry out the procf 7 ess each of the tanks 1 2 is chargedwith three 1. 3O30PbSO4+88ONaHO:

The clear solution containing sodium plumbite and sodium sulfate is thenrun from tank 1, through pipe 6, into tank 7 and thence delivered bypipe 8, ejector 9, and pipe 10 into the second treating-tank 2. The leadhydroxid which has settled to thebottom of tank 1 is Washed with water,and the washings are also introduced into the tank 2. Thesodium plumbitethus introduced into the tank 2 reacts with a portion of the leadsulfate therein, with the production of lead hydroxid, basic leadsulfate and sodium sulfate. This reaction may be represented by.

the following formula:

II. 321Na2PbO2+ 909PbSO1: 24:1PbHzOz-l- 8471 1011202; QPlOSOrl142N32SO4.

When the contents of the tank'2 show no reaction with red litmus, thesolution is drawn off and the sodium sulfate therein derived both fromthe sodium hydroxid employed in tank 1 and from the sodium plumbitedecomposed in tank 2 is drawn off and recovered as Glaubers salt. Theinsoluble residue in tank 2, containing lead hydroxid, basic leadsulfate, and unconverted lead sulfate, is then analyzed, and an aqueoussolution of sodium hydroxid, containing a proportionate excess of sodiumhydroxid to entirely decompose the basic lead sulfate and unchanged leadsulfate, is added. The contents of the tank is then heated for one hour,the reaction between the basic sulfate and alkali hydroxid beingrepresented by the following formula:

The insoluble material is allowed to settle, and the clear solution isrun into tank 7 The residue is washed with water and the washings arealso run into tank 7 The lead hydroxid may be withdrawn from tanks 1 2,but is preferably dissolved in sufficient acetic acid to form a basicsolution and heated. Any iron and coloring-matters therein are thusprecipitated, and the acetate can be directly employed for themanufacture of ch rome-yellow. After the tanks 1 2 have been emptied oftheir contents they are recharged with lead sulfate. The solution ofsodium plumbite and sodium sulfate drawn from the tank 2 into the tank 7is thence deliveredthrough the pipes 8 11 into the tank I, an excess ofsodium hydroxid is added, and the original cycle of operations isrepeated.

I claim 1. The process of converting lead sulfate into lead hydroxid,which consists in treating lead sulfate with an excess of an alkalihydroxid and directly producing lead hydroxid and a solution containinglead, separating said 'lead hydroxid and solution, and treating saidsolution with another portion of lead sulfate, as set forth.

2. The process of converting lead sulfate into lead hydroxid, whichconsists in treating lead sulfate with an excess of an alkali hydroxidand directly producing lead hydroxid and a solution containing lead,separating said lead hydroxid and solution, treating said solution withanother portion of lead sulfate, thereby producing a basic lead sulfate,and decomposing said basic lead sulfate with an alkali hydroxid, as setforth.

3. The process of converting lead sulfate into lead hydroxid, whichconsists in treating lead sulfate with an excess of an alkali hydroxidand directly producing lead hydroxid and a solution containing lead,separating said lead hydroxid and solution, causing said solution toreact on another portion of lead sulfate, thereby precipitating the leadin solution as basic lead sulfate, and treating the re sulting mixtureof lead sulfate and basic lead sulfate with a solution containing anexcess of an alkali hydroxid, as set forth.

4:. The process of converting lead sulfate into lead hydroxid, whichconsists in treating lead sulfate with an excess of an alkali hydroxidand directly producing lead hydroxid and a solution containing lead,separating said lead hydroxid and solution, causing said solution toreact on another portion of lead sulfate, thereby precipitating the leadin solution as basic lead sulfate, treating the resulting mixture oflead sulfate and basic lead sulfate with a solution containing an excessof an alkali

